Minimally invasive surgery (xe2x80x9cMISxe2x80x9d) techniques reduce the amount of extraneous tissue that are damaged during diagnostic or surgical procedures, thereby reducing patient recovery time, discomfort, and deleterious side effects. It is estimated that 7,000,000 surgeries performed each year in the United States can be performed in a minimally invasive manner. However, only about 1,000,000 of the surgeries currently use these techniques, due to limitations in minimally invasive surgical instruments and techniques and the additional training required to master them.
Advances in minimally invasive surgical technology could have a dramatic impact. The average length of a hospital stay for a standard surgery is 8 days, while the average length for the equivalent minimally invasive surgery is 4 days. Thus the complete adoption of minimally invasive techniques could save 24,000,000 hospital days, and billions of dollars annually in hospital residency costs alone. Patient recovery times, patient discomfort, surgical side effects, and time away from work are also reduced with minimally invasive surgery.
The most common form of minimally invasive surgery is endoscopy. A common form of endoscopy is laparoscopy, which is minimally-invasive inspection and surgery inside the abdominal cavity. In standard laparoscopic surgery, a patient""s abdomen is insufflated with gas, and cannula sleeves are passed through small (approximately xc2xd inch (1 cm.)) incisions to provide entry ports for laparoscopic surgical instruments.
The laparoscopic surgical instruments generally include a laparoscope for viewing the surgical field, and working tools, such as clamps, graspers, scissors, staplers, and needle holders. The working tools are similar to those used in conventional (open) surgery, except that the working end of each tool is separated from its handle by an approximately 12-inch long extension tube.
To perform surgical procedures, the surgeon passes instruments through the cannula and manipulates them inside the abdomen by sliding them in and out through the cannula, rotating them in the cannula, levering (i.e., pivoting) the instruments in the abdominal wall and actuating end effectors on the distal end of the instruments. The instruments pivot around centers of rotation approximately defined by the incisions in the muscles of the abdominal wall. The surgeon observes the procedure by a television monitor, which displays the abdominal worksite image provided by the laparoscopic camera.
Similar endoscopic techniques are employed in arthroscopy, retroperitoneoscopy, pelviscopy, nephroscopy, cystoscopy, cisternoscopy, sinoscopy, hysteroscopy and urethroscopy. The common feature of all of these minimally invasive surgical techniques is that they generate an image of a worksite within the human body and pass specially designed surgical instruments through natural orifices or small incisions to the worksite to manipulate human tissues and organs, thus avoiding the collateral trauma caused to surrounding tissues, which would result from creating open surgical access.
There are many disadvantages of current minimally invasive surgical technology. First, the video image of the worksite is typically a two-dimensional video image displayed on an upright monitor somewhere in the operating room. The surgeon is deprived of three-dimensional depth cues and may have difficulty correlating hand movements with the motions of the tools displayed on the video image. Second, the instruments pivot at the point where they penetrate the body wall, causing the tip of the instrument to move in the opposite direction to the surgeon""s hand. Third, existing MIS instruments deny the surgeon the flexibility of tool placement found in open surgery. Most laparoscopic tools have rigid shafts and are constrained to approach the worksite from the direction of the small incision. Those that include any articulation have only limited maneuverability. Fourth, the length and construction of many endoscopic instruments reduces the surgeon""s ability to feel forces exerted by tissues and organs on the end effector of the tool.
Overcoming these disadvantages and achieving expertise in endoscopic procedures requires extensive practice and constant familiarization with endoscopic tools. However, despite surgeons"" adaptation to the limitations of endoscopic surgery, the technique has brought with it an increase in some complications seldom seen in open surgery, such as bowel perforations due to trocar or cautery injuries. Moreover, one of the biggest impediments to the expansion of minimally invasive medical practice remains lack of dexterity of the surgical tools and the difficulty of using the tools.
In a tangentially related area, telesurgery systems are being developed to increase a surgeon""s dexterity as well as to allow a surgeon to operate on a patient from a remote location. xe2x80x9cTelesurgeryxe2x80x9d is a general term for surgical systems where the surgeon indirectly controls surgical instrument movements rather than directly holding and moving the tools. In a system for telesurgery, the surgeon is provided with an image of the patient""s body at the remote location. While viewing the three-dimensional image, the surgeon manipulates a master device, which controls the motion of a servomechanism-actuated slave instrument, which performs the surgical procedures on the patient. The surgeon""s hands and the master device are positioned relative to the image of the operation site in the same orientation as the slave instrument is positioned relative to the act. During the operation, the slave instrument provides mechanical actuation and control of a variety of surgical instruments, such as tissue graspers, needle drivers, etc., which each perform various functions for the surgeon, i.e., holding or driving a needle, grasping a blood vessel or dissecting tissue.
Such telesurgery systems have been proposed for both open and endoscopic procedures. An overview of the state of the art with respect to telesurgery technology can be found in xe2x80x9cComputer Integrated Surgery: Technology and Clinical Applicationsxe2x80x9d (MIT Press, 1996). Prior systems for telesurgery are also described in U.S. Pat. Nos. 5,417,210, 5,402,801, 5,397,323, 5,445,166, 5,279,309 and 5,299,288.
Proposed methods of performing telesurgery using telemanipulators also create many new challenges. One is presenting position, force, and tactile sensations from the surgical instrument back to the surgeon""s hands as he/she operates the telesurgery system, such that the surgeon has the same feeling as if manipulating the surgical instruments directly by hand. For example, when the instrument engages a tissue structure, bone, or organ within the patient, the system should be capable of detecting the reaction force against the instrument and transmitting that force to the surgeon. Providing the instrument with force reflection helps reduce the likelihood of accidentally damaging tissue in areas surrounding the operation site. Force reflection enables the surgeon to feel resistance to movements of the instrument when the instrument engages tissue. A system""s ability to provide force reflection is limited by factors such as friction within the mechanisms, gravity, the inertia of the surgical instrument and the size of forces exerted on the instrument at the surgical incision. Even when force sensors are used, inertia, friction and compliance between the motors and force sensors decreases the quality of force reflection provided to the surgeon.
Another challenge is that, to enable effective telesurgery, the instrument must be highly responsive and must be able to accurately follow the rapid hand movements that a surgeon may use in performing surgical procedures. To achieve this rapid responsive performance, a surgical servomechanism system must be designed to have an appropriately high servo bandwidth. This requires that the instrument have low inertia. It is also preferable if the system can enhance the dexterity of the surgeon compared to standard endoscopic techniques by providing more degrees-of-freedom (xe2x80x9cDOFsxe2x80x9d) to perform the surgery by means of an easily controlled mechanism. By more DOFs, it is meant more joints of articulation, to provide more flexibility in placing the tool end point.
Another challenge is that to enable minimally invasive surgery, the instrument must be small and compact in order to pass through a small incision. Typically MIS procedures are performed through cannulas ranging from 5 mm. to 12 mm. in diameter.
Surgeons commonly use many different tools (sometimes referred to herein as end-effectors) during the course of an operation, including tissue graspers, needle drivers, scalpels, clamps, scissors, staplers, etc. In same cases, it is necessary for the surgeon to be able to switch, relatively quickly, from one type of end effector to another. It is also beneficial that effectors be interchangeable (even if not very quickly), to reduce the cost of a device, by using the portion of the device that does not include the end effector for more than one task.
However, the mass and configuration of the effector affects the dynamics and kinematics of the entire system. In typical cases, the effector is counter balanced by other elements of the system. Thus, to the extent that effectors are interchangeable, this interchangeability feature should be accomplished without rendering the remainder of the system overly complicated.
What is needed, therefore, is a servomechanical surgical apparatus for holding and manipulating human tissue under control of a teleoperator system.
It would also be desirable to provide a servomechanical surgical apparatus that can-provide the surgeon with sensitive feedback of forces exerted on the surgical instrument.
It would further be desirable to provide a servomechanical surgical apparatus that is highly responsive, has a large range of motion and can accurately follow rapid hand motions that a surgeon frequently uses in performing surgical procedures.
It would still further be desirable to provide a servomechanical surgical apparatus that increases the dexterity with which a surgeon can perform endoscopic surgery, such as by providing an easily controlled wrist joint.
It would also be desirable to provide a dexterous surgical apparatus having a wrist with three independent translational degrees-of-freedom, which can provide force feedback with respect to those three degrees of freedom.
It would still further be desirable to provide a surgical instrument having a wrist mechanism for minimally invasive surgery, which is suitable for operation in a telemanipulator mechanism.
It would additionally be desirable to provide a servomechanical surgical apparatus that has easily interchangeable end effectors, the exchange of which does not require significant adjustments to the kinematic and dynamic control of the apparatus, thereby allowing different end effectors to be used on one base unit, either during the same operation, or, at least, during different operations.
To some extent, the inventions discussed in the three patent applications by the present inventors Madhani and Salisbury that are incorporated herein by reference, address these goals. The invention described herein further satisfies these goals.
A preferred embodiment of the invention is a robotic apparatus comprising: seven actuators, M0, M1, M2, M3, M4, M5 and M6; a support; an end effector link having an effector reference point; and a linkage of links and joints between the support and the end effector link reference point. The linkage comprises: three macro joints, coupled to each other in series, one of which joint 0 is coupled directly to the support, the joints operating to provide three macro translation DOFs to the end effector link reference point, which macro DOFs are characterized by a relatively large range of motion; and four additional joints, designated micro joints coupled in series with the three macro joints and coupled to each other in series, one of which micro joints, joint 6 being coupled directly to the end effector link reference point, the four micro joints operating to provide three micro translation DOFs to the end effector link reference point, which micro DOFs are characterized by a relatively small range of motion as compared to the macro DOFs and where the micro DOFs are redundant with the macro DOFs with respect to translation. For each of the actuators, there is a transmission, coupled to the actuator and coupled to at least one of the seven (four micro plus three macro) joints, thereby actuating each of the seven joints.
The actuators are mounted such that during translation of the effector link reference point, the actuators move through no more than two macro DOFs, and such that they move through no micro DOFs. The linkage comprises macro links that are movable only with the macro DOFs, and other, micro links that are movable through both the macro DOFs and the micro DOFs. The micro links each have a relatively low inertia, as compared to the inertia of any one of the macro links.
According to another preferred embodiment, the three macro joints comprise: a joint 0, a rotary joint about an axis A0, coupled to the support and to a joint 0 link; joint 1, a rotary joint, about an axis A1, orthogonal to the axis A0 and coupled to the joint 0 link and to a joint 1 link; and joint 2, a translational joint along an axis A2, spaced from and perpendicular to the axis A1 and coupled to the joint 1 link and to a joint 2 link.
According to yet another preferred embodiment, the four micro joints comprise: joint 3, a rotary joint about an axis A3, that is parallel to the Axis A2, coupled to the joint 2 link and to an elongated hollow shaft link; joint 4, a rotary joint about an axis A4, that is perpendicular to the axis A3, coupled to the hollow shaft link and to an extension link; joint 5, a rotary joint about an axis A5, that is spaced from and parallel to the axis A4, coupled to the extension link and to an effector support link; and joint 6, a rotary joint about an axis A6 that is spaced from and perpendicular to the axis A5, coupled to the effector support link and to the end effector link.
There may also be an eighth actuator M7 and an additional joint, which couples an end effector jaw link to the effector support link, to rotate around an axis A7, which jaw link is operable to move toward and away from the end effector link, thereby effectuating gripping of an object therebetween.
According to still another preferred embodiment, a total of six effector cable tension segments extend from various components of the end effector, through the elongated hollow link.
A preferred embodiment of a micro macro manipulator as described above also includes a controller that controls the manipulator according to an Inverse Jacobian controller, where the gains of the macro freedoms are adjusted to be much larger than the gains of the micro freedoms, on the order of the ratio of the inertias thereof.
According to a related preferred embodiment, the transmission comprises the six cables and a base set of transmission elements, which are each coupled directly to one of the actuators; and a releasable couple, which couples an individual one of the six effector cable tension segments to an individual one of the base set of transmission elements. The base transmission elements may include cable segments.
According to still another preferred embodiment, any one of the embodiments of the invention outlined above may constitute a slave actuator unit. A master actuator unit may be provided, having a master linkage, having: a master reference point, coupled to a master ground support through a plurality of master links and master joints; and a plurality of master actuators, coupled to the master linkage to actuate the master reference point. A controller is coupled to the slave unit actuators, configured to control the slave according to an Inverse Jacobian controller. Another controller is coupled to the master actuators, configured to control the master according to a Jacobian Transpose controller.
The macro freedom gains and the micro freedom gains are preferably chosen such that the inertia of the macro freedoms is suppressed in any forces felt at the master reference point.
According to yet another preferred embodiment, the slave unit linkage is characterized by a number X of DOFs, X being at least seven DOFs and the master unit linkage is characterized by a number Y of DOFs where Y is at least one fewer than X. According to this embodiment, the slave controller can be configured to resolve a redundancy in control due to the difference between the X DOFs of the slave unit and the fewer Y DOFs of the master unit by applying a cost function to a range of possible joint configurations, each of which provide the same location of the end effector link reference point, and minimizing the cost function.
Another preferred embodiment of the invention is a robotic apparatus having a base unit and an effector unit. The base unit has a support, an actuator M0 and a base linkage, connected to the support, and to the effector unit. The base linkage comprises a drivable member D0, drivable by the actuator M0 through a DOF DOF0, such that the effector end of the base linkage is drivable through the DOF0. The base linkage also includes a drivable member D1, movable through the DOF0 with the drivable member D0, and also through another DOF DOF1. An actuator M1, drives the drivable member D1 through the DOF1, such that the effector end of the linkage is drivable through the DOF1. An actuator set, which is drivable with the drivable member D1 through the DOF1, comprises a plurality of K actuators. Each of the plurality K has one terminal thereof fixed relative to the drivable member D1, and one terminal thereof free to move through one DOF relative to the drivable member D1. The base further includes a plurality K of base transmission elements, each of the plurality K coupled with a free terminal of one of the K actuators, and each of the base transmission elements including an effector transmission coupling site. This base, alone, is a preferred embodiment of the invention. It can also be used, in combination with the effector unit, described as follows.
The effector unit has a base end, connected to the base linkage, an end effector and an effector linkage comprising a plurality of links and joints, which effector linkage extends from the base end to the end effector. For each joint, an effector transmission element is connected to a link that is adjacent the joint and that also has a base coupling site distant from the link connection. For each effector transmission element, a transmission clamp connects the effector transmission element to a corresponding base transmission element, thereby coupling the effector transmission element, and thereby its associated link, to a movable terminal of one of the plurality K of actuators.
According to such a preferred embodiment, the end effector has N=K+2 DOFs under action of the plurality K actuators and the two actuators M0 and M1, none of which plurality K actuators are movable through any of the N DOFs other than the DOF0 and DOF1.
The end effector just described may also be used with other types of base supports. A releasable couple between the transmission elements of the base and the effector completes the transmission.
It is also a preferred embodiment of the invention to provide, coupled to the Inverse Jacobian controller and to the Jacobian Transpose controller, an environment position sensor, arranged to generate a signal that corresponds to the translational position of a reference point in an environment in which the slave may reside. The Inverse Jacobian controller further commands the macro freedom actuators and micro freedom actuators to move the effector reference point in concert with the environment reference point. The Jacobian Transpose controller further is configured to command the master to move the master reference point to follow only motion of the effector reference point that does not correspond to motion of the environment reference point. This presents the effect to a user who is in contact with the master reference point that the effector is interacting with an environment that is substantially motionless. Thus, a surgeon engaging the master can use the slave to operate on a beating heart, while perceiving the heart as stationary.
According to yet another preferred embodiment of the invention, at least two base transmission elements of a base, such as is described above, comprise cables and at least two corresponding effector transmission elements comprise cables. An extent of the at least two base transmission elements extend substantially parallel to each other and an extent of the at least two effector transmission elements extend substantially parallel to each other. The extent of each of the at least two effector transmission elements that extends substantially parallel to each other is parallel to and adjacent to the extent of the corresponding of the at least two base transmission elements that extends substantially parallel to each other. The adjacent extents of corresponding effector and base transmission elements can be clamped to each other such that motion of the base transmission elements is transmitted to the effector transmission elements. There can be any number of pairs of cables so clamped to each other.
Yet another preferred embodiment of the invention is simply a couple between an actuator unit and an effector unit of a robotic apparatus. The actuator unit, comprises an actuator that actuates a tension bearing transmission element, comprising a tension segment that is arranged to follow a straight line for a portion of its path [PAS]. The effector unit comprises a movable end effector link, coupled to a tension bearing transmission element, comprising a tension segment that is arranged to follow a straight line for a portion of its path PES, which PES is arranged parallel to the portion PAS. A releasable couple clamps the portion PAS of the actuator unit transmission element to the portion PES of the effector unit transmission element, thereby releasably coupling the actuator to the end effector link. There can be a large number of parallel transmission elements so linked together, for instance at least six.
Still another preferred embodiment of the invention is An actuator set comprising a plurality of actuators, each actuator having a first and a second terminal, the second of which is rotatable about an output axis relative to the first, which second terminal is adapted to engage a transmission element, each of the output axes having a component thereof that is parallel. For each of the actuators, a transmission element is looped around the rotatable terminal, forming two tension segments. For each of the transmission elements there are a pair of low friction circular surfaces, along each of which passes one of the two tension segments. The pair of circular surfaces are centered about an axis that is substantially perpendicular to a component of the output axis of the respective actuator. There is also turnaround located along the path of the transmission element between the points at which it engages each pulley of the pair, such that tension is maintained on the transmission element. The axes of the actuators may be parallel.
Yet another preferred embodiment of the invention is a method of controlling a manipulator, as described above, comprising the steps of: coupling a controller to the manipulator actuators; configuring the controller to control the manipulator according to an Inverse Jacobian controller; commanding the micro freedom actuators M3, M4, M5 and M6 with micro freedom gains; and commanding the macro freedom actuators M0, M1 and M2 with macro freedom gains that are much larger than the micro freedom gains.
The method may further include sizing the macro and micro freedom gains such that the ratio of a representative one of the micro freedom gains to a representative one of the macro freedom gains is on the order of a ratio of a representative one of the micro freedom inertias to a representative one of the macro freedom inertias.
A preferred embodiment of the invention also includes controlling such a manipulator as a slave apparatus, by a master apparatus, including the further step of configuring a Jacobian Transpose controller to command the master to move the master reference point to follow motion of the effector reference point.
A final preferred embodiment of the invention is a method of controlling such a manipulator, when the slave unit linkage is characterized by a number X of DOFs, X being at least seven DOFs and the master unit linkage is characterized by a number Y of DOFs where Y is at least one fewer than X, the method further comprising the step of resolving a redundancy in control due to the difference between the X DOFs of the slave unit and the fewer Y DOFs of the master unit by applying a cost function to a range of possible joint configurations, each of which provide the same location of the end effector link reference point, and minimizing the cost function.